1 Introduction

Presbyopic patients spend money and time to have contact lens monovision or laser vision correction monovision. So why do we cataract surgeons not use intraocular lenses (IOLs) more often to create monovision? For a cataract patient with a desire for spectacle independence after surgery, there are different ways to create monovision. If it were like buying a car, where the prospective buyers can try different models before they make a choice, then IOL monovision might be favored by many more, if not the vast majority of patients, due to the quality of vision from monofocal lenses, low cost, convenience of back up of glasses if needed, and close to negligible downsides.
Monovision as a method of prescribing optical aids was first proposed in 1958 by Richard West-smith. The first clinical report was from Fonda in 1966. The first known IOL monovision paper was published by Boerner and Thrasher in 1984. IOL monovision is now the most common surgical management of presbyopia for cataract patients. IOL monovision not only can meet patient needs for spectacle independence, but can also build up one’s surgical practice and lay a strong foundation for premium IOL refractive cataract surgery. Integrating IOL monovision into premium IOL practice is very helpful or even essential for successful premium refractive cataract surgery. Crossed IOL monovision can be used to rescue one’s outcome when the first eye refractive target is missed with accommodative and extended depth of focus IOLs.

Keywords: IOL monovision, pseudophakic monovision, refractive cataract surgery, premium IOL and IOL monovision, clinical outcome of IOL monovision, nighttime driving and monovision, depth perception and monovision, patient satisfaction and monovision, pseudophakic monovision book, IOL monovision book

1.1 Introduction

Monovision is a term used when one eye is intentionally corrected for far and the fellow eye for near. Monovision is a misnomer. It gives the impression of using one eye only or that the two eyes do not work together. The name itself potentially can be a barrier, preventing some patients from considering it as a presbyopia management modality. Blended vision may be a better term. When both eyes work together, monovision provides increased depth of focus but maintains good binocular vision with decreased spectacle independence.

1.2 Why This Book Was Written?

1.2.1 Killing Two Birds with One Stone

People who do not want to wear reading glasses, or cannot wear bifocals, may intentionally use monovision with contact lenses, or may spend thousands of dollars to have laser corneal refractive surgery correction with monovision. Many studies in the literature have demonstrated its validation. Why then do we not use intraocular lenses (IOLs) more often for monovision, one stone killing two birds, when we do cataract surgery? That is the rationale for IOL monovision.

1.2.2 One of the Most Popularly Used Modalities

Increasingly, premium IOLs have become available in the last two decades with the same goal of increasing spectacle independence after cataract surgery, and most of them do well with high patient satisfaction. IOL monovision, however, still stands out with quality of vision, easy adaptation, fewer complications, and less out-of-pocket cost for patients. Modest monovision continues to be an attractive presbyopic solution and, in our opinion, should be considered a “premium” solution. It requires expert surgery, lens selection, and the utilization of toric implants or corneal incisions to reduce astigmatism. From a surgeon’s perspective, myopic defocus is one of the two bases of refractive cataract surgery, as expressed in the pyramid scheme in image Fig. 1.1. From a patient perspective, choosing the type of IOL is not like buying a car, where one can try different models and then pick the best. No one will argue that monovision is perfect, with compromises such as fine stereovision, but the truth is that in real life, the negative impact is minimal. (See the section “What Benefits Can IOL Monovision Bring to Your Practice?”)

Before we have an ideal accommodating IOL, IOL monovision is still one of the best choices, if not the best, in the management of presbyopia among the cataract population. IOL monovision was the number one modality for the management of presbyopia in cataract surgery according to the 2013 ASCRS clinical survey.1 What is more, the trend of choosing IOL monovision increased between 2013 and 2014.2

1.2.3 Residency Education

Most ophthalmology residencies in the United States and the rest of world do not provide formal training for monovision. IOL monovision may not be easy to adopt if one never intentionally has tried it, even though he or she might be a very experienced cataract surgeon. The questions we sometimes get are “How do you know who are good candidates and who are not?” “How much anisometropia should I target?” “What are the contraindications?” From our own learning curve in the practice of IOL monovision, we wished there was a book available which could have provided us some suggestions, pearls, and pitfalls so that we did not have to learn many lessons the hard way.

1.2.4 Making One’s Surgical Practice Prosperous

A surgeon who does a large proportion of pseudophakic monovision in cataract surgery for those who desire glasses independence can be expected to have a busy and happy, no-advertisement-needed, prosperous practice, mainly from word of mouth of satisfied patients.

The above are the four main reasons why this book was written. To our knowledge, this is the first book exclusively designated to address IOL monovision.

1.3 A Brief History of Monovision

Monovision as a method of prescribing optical aids was first proposed in 1958 by Richard Westsmith, MD, of San Mateo, California, for presbyopic monocular contact lens wearers.3 In his paper, he revealed that he had a contact lens of + 1.50 D for his own left eye for reading. He did not need any correction for distance with a vision of 20/20 in each eye. He was unable to tolerate a bifocal for his office work. With monocular contact lens monovision, Westsmith experienced “I have had the contact lens about a month now and I find that I am able to wear it comfortably all day and I have complete clarity of near vision. I am undisturbed by the slight blur in my left eye at distance. With the corneal lens in place, my vision in the left eye is 20/50. However, with both eyes I am able to read J1 at 18 inches. There is no trouble with the ophthalmoscope, retinoscope, or slit lamp.”

The first clinical report was from Fonda in 1966 with 13 cases of monovision corrected by spectacles and contact lenses.4 He also described himself as a monovision user. “I have been wearing a + 3.00 D reading addition before my right eye, and a + 1.50 D reading addition before my left eye for two years. I adjusted immediately to this difference, which does not affect my reading comfort regardless of the circumstances or duration of reading. I can wear a + 2.50 reading addition before one eye and no addition before the other. I have worn a + 2.50 D reading addition before both my dominant left eye and nondominant right eye on different occasions which was accepted equally well. I was conscious of the new correction for less than four hours. I never experienced diplopia, and evidenced fusion by the four-dot test and the Wirt stereo-quantitative test.”

The first known pseudophakic monovision paper was published by Boerner and Thrasher in 1984.5 In that study, among the 100 IOL monovision patients, the need to have bifocals after the surgery decreased 50%. And IOL monovision is now the most common surgical management of presbyopia for cataract patients.1,2

For the last half century, monovision has been increasingly used for presbyopia management with an impressive success rate. There are different ways to provide monovision: spectacles, contact lenses, refractive lasers, intraocular implants, etc. This book concentrates on the discussion of IOL monovision, or pseudophakic monovision, but at the same time, other methods will be briefly discussed, since most of the monovision studies in the literature were with contact lens and laser vision correction. IOL monovision is barely discussed in the literature considering how widely it is used in our profession.

1.4 What Benefits Can Pseudophakic Monovision Bring to Your Practice?

1.4.1 To Meet Patients’ Needs

We used to be satisfied with regular telegraphy and then telephones, but now we are happier with smart phones and the internet. Science and technology will continue to advance. Cataract surgery was simply a vision rehabilitation procedure a few decades ago, but it is not so any more. Just from a spectacle independence point of view, our clinical survey (all the 441 cataract patients’ 697 eyes in 2016) noted that 44% of our cataract patients would like to have some level of freedom from glasses and nearly one-fourth would like to have complete glasses independence. If financial factors were not considered, these percentages would be expected to be much higher.

1.4.2 To Build Up Practice

About 10 years ago, one of my junior staff members called me (F. Z.) at home. He was wondering why his practice was not as busy since he had joined our health system a few years earlier and he wanted me to give him advice in terms of what made my practice very busy while we were in the same geographic area. My answer was “Do your best to satisfy your patients and do IOL monovision.” Our own comparative prospective studies proved slightly better overall performance and satisfaction in IOL monovision than multifocal IOL patients.6,7 When compared with premium IOLs, IOL monovision has a few obvious advantages:

1. High patient satisfaction. As mentioned below, our 10-year IOL monovision review with a de-identified survey noted 97% satisfaction. Anecdotal experience of IOL monovision success from Bill Maloney, one of the IOL monovision pioneers, was 99%.8

2. Use of monofocal IOLs with high vision quality. Many fewer complaints and very low IOL explantation rate. Downside in real life is negligible.

3. Back up glasses are very handy when the need arises to have full binocular vision.

4. Less or no direct patient cost.

These advantages are significant and word of mouth is the most powerful advertisement in the community. If one’s surgical complications are also very low, then one can expect a busy practice.

Overall, IOL monovision clinical outcomes can be excellent if we master all the key steps. We did a de-identified survey of all of our IOL monovision patients over 10 years. All 5,660 charts of consecutive cataract surgical cases performed by F. Z. from January 2005 to December 2014 were reviewed (followed up to August 2015). Among 359 qualified cases, 194 were enrolled, 30 had died, 48 declined participation, and the remaining 87 could not be contacted with at least three phone calls. Among the 48 who declined participation, the vast majority did not have regular postoperative follow-up.

The mean age was 72.5 years. The subjects were 135 females (69.6%) and 59 males (30.4%). Mean follow-up was nearly 3 years (35 months). Mean distance vision without correction for the distance eye was 20/24.7 and mean near vision without correction for the near eye was 20/28.1. Mean anisometropia was 1.30 D.

To ensure accountability and reliability, it was clearly described in the introduction of the survey letter to each patient that the surgeon is not going to have access to the survey and thus to kindly provide honest opinion. All the original data of the survey were handled by a research assistant, and the statistics were then performed by an independent statistician. The four brief outcomes of the survey are shown as follows (image Fig. 1.2, image Fig. 1.3, imageFig. 1.4, image Fig. 1.5).

Feb 18, 2020 | Posted by in OPHTHALMOLOGY | Comments Off on Introduction

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